Holding device for the inner seal of a fluid-operated percussion drive

ABSTRACT

An apparatus having a housing ( 5 ) that shields a front of a percussion drive ( 1 ) against the environment, and into which a drive driven tool ( 3 ) projects. An exchangeable outer seal ( 10 ) is disposed at the housing opening ( 6   c ) for the tool ( 3 ), surrounds the tool transversely to its longitudinal axis ( 3   a ) with spacing, and is moveable in this transverse direction. An inner seal ( 11 ) is disposed behind the outer seal ( 10 ), and rests elastically against the tool ( 3 ) outside of its tool guide ( 2 ). The inner seal ( 11 ) is exchangeably secured to an elastic extension ( 12 ) of the tool guide ( 2 ) that surrounds the percussive tool ( 3 ) in the region of the inner seal ( 11 ) with a spacing larger than the largest transverse displacement of the tool ( 3 ). The extension ( 12 ) is an independent, elastic support that forms a detachable connection with the tool guide ( 2 ) at one end.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is based on and claims the priority date ofGerman Application No. 102 02 648. 3, filed on Jan. 23, 2002, which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] The invention relates to a holding device for the inner seal of afluid-operated percussion drive, having a housing part that shields thepercussion drive, at least at the front, against the environment, andinto which a percussive tool driven by the drive projects; anexchangeable outer seal, which is disposed at the opening provided inthe housing part for the tool, the seal surrounding the tooltransversely to its longitudinal axis with at least some spacing, andbeing embodied to move in this transverse direction; and having an innerseal, which is disposed behind the outer seal, seen counter to thedirection of action of the tool, and rests in an elastic manner againstthe tool, outside of its guide. The inner seal is secured, so as to beexchanged, to an extension of the tool guide in the direction of action.This extension surrounds the percussive tool in the region of the innerseal, with a spacing that is larger than the largest possible transversedisplacement of the percussive tool.

[0003] DE-A1-196 28 815, which was published prior to this application,discloses a generic holding device in connection with a protectivedevice in a fluid-operated percussion drive. The known protective deviceis particularly intended to improve the functioning reliability of thepercussion drive by decreasing the wear in the region of the tool guide,as well as to decrease repair and maintenance costs. The deviceaccomplishes these objectives in that the outer seal—formed, forexample, as a movably seated cross slide—simultaneously functions as amechanical shield and an advance scraper, while the inner seal disposedbehind the outer seal is intended to prevent the penetration of finecontaminants into the region of the tool guide.

[0004] The percussion drive can have an arbitrary form, provided that itincludes a percussive tool that can be moved back and forth in a toolguide, driven by the percussion drive.

[0005] The known protective device is capable of considerably improvingthe functioning reliability of the percussion drive, but it isdisadvantageous that the inner seal is secured to an extension of thetool guide that is an integral component of the tool guide itself. Inthe event of tool breakage, which cannot always be avoided, and mayoccur near the outer end segment of the outer tool guide, the extensionof the tool guide may be destroyed or so heavily damaged that the toolguide must be disassembled and replaced, which is usually a cost- andlabor-intensive process.

[0006] Because the production of the tool guide with the extension isrelatively expensive, this guide is only used in fluid-operatedpercussion drives having an inner seal that is disposed behind the outerseal. Accordingly, different tool guides must be produced for percussiondevices of the same structural size but different designs.

SUMMARY OF THE INVENTION

[0007] It is the object of the invention to improve the known protectivedevice with respect to the holding device for the associated inner seal,and therefore make the percussion device more economically feasible.

[0008] In particular, the novel holding device is to be designed suchthat, in the event of serious malfunctions, especially tool breakage,the tool guide need not be disassembled and exchanged, provided that itis not also affected by the malfunction.

[0009] The above object generally is achieved according to the presentinvention by an apparatus comprising: a fluid-operated percussion drive;a housing part that shields the percussion drive, at least at the front,against the environment, and into which a percussive tool driven by thedrive projects axially into a tool guide of the drive; an exchangeableouter seal disposed at an opening provided in the housing part for thetool, with the seal surrounding the tool, transversely to itslongitudinal axis, with at least some spacing, and being seated formovement in the transverse direction; an inner seal disposed behind theouter seal, when seen counter to the direction of action of the tool,and resting in an elastic manner against the tool, outside of saidguide, with the inner seal being secured, so as to be exchangeable, toan axial extension of the tool guide in the direction of the action ofthe tool, said extension surrounding the percussive tool in the regionof the inner seal, with a spacing that is larger than the largestpossible transverse displacement of the percussive tool in the housing;and wherein: the extension is an independent, elastic support elementthat, on its rear side facing away from the inner seal, has a beginningsegment that forms a detachable connection with a receiving segment ofthe tool guide in the longitudinal and transverse directions; and, theextension latches in the receiving segment of the tool guide that isdesigned to secure the extension in a snap connection.

[0010] The essential concept of the invention lies in configuring theelastomer extension for supporting the inner seal as an independent,elastic support element which, on its rear side or end facing away fromthe inner seal, forms a detachable connection with the tool guide thatis similar to a snap connection. Here, the extension latches in thereceiving segment of the tool guide that is designed to secure it. Inother words, the inner seal is connected to the tool guide, and theextension, which can be detached from the tool guide, is disposedbetween the seal and the guide. Furthermore, the elastic deformabilityof the extension allows it to engage the receiving segment designed tosecure it, and maintain the connection through its elastic behavior,provided that no external forces are present that could overcome theretaining forces between the extension and the tool guide.

[0011] Due to the elasticity of the extension, the extension and thereceiving segment of the tool guide are adapted to one another such thatthe extension is immovably connected to the receiving segment afterbeing brought into the segment with the deformation necessary forlatching, provided that no measures are undertaken to initiate theseparation of the extension from the segment, or no circumstances occurthat could trigger correspondingly large forces.

[0012] If tool breakage occurs outside of the outer end segment of thetool guide, the broken piece typically only damages the extension andthe inner seal, so only the two aforementioned parts must be exchanged.The tool guide itself need not be disassembled.

[0013] It may be that the force originating from the broken piece merelycauses the connection between the receiving segment of the tool guideand the extension to be broken; consequently, the extension may belatched to the receiving segment again and reused after the inner sealhas been exchanged.

[0014] It is greatly significant that the elastic properties of theextension allow it to be inserted into the correspondingly adaptedreceiving segment of the tool guide and maintain the produced connectionautomatically, so to speak.

[0015] In accordance with the above discussion, it is especially simpleto meet the requirements on the extension by using a thermoplasticelastomer, notably polyurethane. Of course, the extension can also beproduced from other materials, should they yield comparable propertiesin the connection considered here.

[0016] The subject of the invention can be expanded to include formingthe connection between the tool guide and the extension to be at leastpartially inside the tool guide, or supporting the extension on theoutside of the tool guide, which faces away from the percussive tool.

[0017] As an alternative, the invention also relates to embodiments inwhich the extension is detachably supported on the inside of the toolguide, which faces the percussive tool.

[0018] In an especially simple embodiment of the subject of theinvention, the tool guide has at least one annular-groove-likedepression as a component of the connection. The elastic deformabilityof the extension allows it to latch in this recess, thereby creating aform-fit and/or a non-positive lockup with the tool guide.

[0019] Depending on the geometric relationships and other operatingconditions, a plurality of annular-groove-like depressions can beprovided, with spacing from one another, in the tool guide. In thisinstance, the extension is supported in the depressions by a pluralityof adapted, annular projections.

[0020] The at least one annular-groove-like depression is preferablyformed on the outside of the tool guide facing away from the percussivetool. The advantage of this arrangement is that the receiving segment ofthe tool guide is in a region of the percussion drive where it is lesslikely to be damaged.

[0021] Within the scope of the invention, the at least oneannular-groove-like depression can, however, also be disposed on theinside of the tool guide facing the percussive tool.

[0022] The effect or operating reliability of the novel holding elementmay be further improved if the annular-groove-like depression isadditionally undercut on at least the side facing the inner seal or theside facing away from it. In such embodiments, the annular-groove-likedepression is partially closed by a circumferential protrusion, so in across-section, the depression has a hollow space with an opening thateither faces the percussive tool or is on the side of the tool guidefacing away from the tool.

[0023] Within the scope of the invention, the annular-groove-likedepression can also be formed as a front-side depression that starts atthe front side of the tool guide facing the inner seal. The advantage ofthis embodiment is that the extension, which has a countersurface thatis adapted to a respective depression, can be connected to the toolguide without being severely deformed.

[0024] The front-side depression is advantageously undercut in thedirection of the tool guide, so in a correspondingly adapted embodimentof the extension, a form-fit connection can be produced using thefront-side depression.

[0025] The operating reliability of the novel holding device can also beincreased, if necessary, by additionally holding the extension inposition in the direction of the receiving segment of the tool guide bymeans of at least one annular securing element. Depending on how thereceiving segment is oriented, the securing element is either pushedonto the outside or inside of the extension and supports the holdingforce originating from the extension itself.

[0026] The annular securing element can essentially have any other formor embodiment, for example, that of a bushing or a helix. The securingelement is preferably formed as a spring element in order to ensure thatthe extension can detach from the tool guide in the event of anunacceptably high force, despite the use of the securing element, andavoid more extensive damage.

[0027] For producing a detachable connection with the receiving segmentof the tool guide, the extension has at least one annular latch, whichextends into the receiving segment of the tool guide.

[0028] In this case, at least one latch of the extension can be embodiedor formed such that it is supported in a non-positive lockup on thereceiving segment. This can be effected in a simple manner bydimensioning the latch to be larger than the annular-groove-likedepression that receives it, so that the latch extends into thedepression with a prestress.

[0029] Of course, it is possible within the spirit of the invention tocombine the embodiments described above.

[0030] In particular, the tool guide can have at least one depression onthe front side, and at least one annular-groove-like depression oneither the outside facing away from the tool or the inside facing thetool, in which instance the extension is equipped with projections thatare adapted to the relevant depressions and are supported in them.

[0031] The holding device can further be formed such that the wallthickness of the extension, with the exception of its beginning segmentthat forms the connection, and its end segment that supports the innerseal, decreases in the direction of the end segment. In the simplestcase, the wall thickness changes in linear fashion. However, it can alsofollow a curved path.

[0032] It can be advantageous to dimension the inner diameter of the endsegment of the extension that supports the inner seal to be larger thanthe inner diameter of the beginning segment that forms the connection.

[0033] The invention is described in detail below by way of embodimentsthat are illustrated schematically in the drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0034]FIG. 1 is a partial section through the lower part of a percussiondrive having an associated housing part that receives an exchangeablecomponent whose outer seal is seated so as to be displaced.

[0035]FIG. 2 is a partial section of the embodiment according to FIG. 1,on an enlarged scale.

[0036]FIG. 3 is a partial section through an embodiment similar to theone in FIG. 2, with the annular-groove-like depression that is formed onthe inside of the tool guide being undercut in the direction of the toolguide.

[0037]FIG. 4 is a partial section in the region of the tool guide, theextension connected to the guide and the inner seal secured thereto, thetool guide being provided with an annular-groove-like depression on itsoutside.

[0038]FIG. 5 is a partial section through an embodiment similar to theone in FIG. 4, with the outside of the tool guide being provided withtwo annular-groove-like depressions that are spaced from one another.

[0039]FIG. 6 is a partial section through an embodiment similar to theone in FIG. 4, in which the annular-groove-like depression that isprovided on the outside of the tool guide is undercut in the directionof the tool guide.

[0040]FIG. 7 is a partial section through an embodiment in which theextension supporting the inner seal is held by an annular-groove-likedepression on the outside of the tool guide, on the one hand, and by anannular-groove-like, front-side depression that originates from thefront side of the tool guide, on the other.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041] Because the rest of the embodiment of the fluid-operatedpercussion drive is not of importance for the realization of theinvention, FIG. 1 only illustrates the lower part 1 of the percussiondrive, in which a tool guide 2 is immovably held. A percussive tool inthe form of a chisel 3 and having the longitudinal axis 3 a is supportedso as to move longitudinally in the guide 2. An arrow 4 indicates thedirection of movement of the chisel 3 in the direction of action. Thependulous movements that the chisel 3 may perform are schematicallyindicated on an exaggerated scale by dashed lines 3 b and 3 c.

[0042] A housing part 5, which detachably receives an exchangeablecomponent 6 at its front side (at the bottom in the figure), is securedas an extension to the lower part 1 of the percussion drive. Forreceiving the exchangeable component 6, the housing part 5 is providedwith a recess 7 that is slightly deeper than the height of thecomponent, and whose diameter is adapted to the diameter of thecomponent. The parts 5 and 6 are detachably secured to one another bypins 8.

[0043] The exchangeable component 6 comprises a front plate 6 a and arear plate 6 b. These plates have a sufficiently large passage 6 c forthe chisel 3, and limit an annular chamber 9 transversely to thelongitudinal axis 3 a. An outer seal in the form of a disk-shaped crossslide 10 is seated to move in this chamber 9.

[0044] The height of the annular chamber 9 in the direction of thelongitudinal axis 3 a is slightly larger than the thickness of the crossslide 10, so the transverse movements of the chisel 3 relative to thehousing part 5 cause the slide to move back and forth as a rigid unit.

[0045] Unlike in the schematic representation of FIG. 1, the wall 10 aof the cross slide 10, which limits the opening for the chisel 3, isformed such that transverse movements of the chisel 3 (indicated by thelines 3 b and 3 c) do not cause the parts 3 and 10 to become misaligned.For this purpose, the wall 10 a has a convex curvature in the directionof the chisel 3 (unlike in the illustration).

[0046] The parts 6 a and 6 b are connected (not shown). Accordingly, theexchangeable part 6 can be installed and removed as a unit with thecross slide 10 seated to move freely therein.

[0047] Inside the housing part 5, an inner seal 11 is disposed behindthe cross slide 10, seen counter to the direction of action (arrow 4).The sealing lip 11 a of the seal rests in an elastic manner against thechisel 3, and acts as a scraper for contaminants that have entered thehousing part 5.

[0048] The inner seal 11 is detachably secured to an extension 12 via asecuring groove 12 b cut into the end segment 12 a of the extension(FIG. 2). In the region of the inner seal 11, the extension 12 surroundsthe chisel 3 at a distance s, which is larger than the largest possibletransverse displacement of the chisel in this region (indicated by thelines 3 b and 3 c).

[0049] To assure proper functioning of the inner seal 11 under differentoperating conditions, the length of the sealing lip 11 a should beselected so that the ratio of its length to the largest possibletransverse displacement of the chisel 3 in the region of the sealing lipis a value greater than 2.

[0050] Unlike in the prior art, the elastomer extension 12 is formed asan independent, elastic support element. Its beginning segment 12 c,which rests on the rear side or end of the extension 12 facing away fromthe inner seal 11, can form a detachable, snap-like connection with acorrespondingly adapted receiving segment 2 a, in the region of thefront side or end 2 b of the tool guide (FIG. 2).

[0051] For this purpose, the receiving segment 2 a is provided with anannular-groove-like depression 13 that is spaced from the front side orsurface 2 b and is oriented transversely to the longitudinal axis 3 a.

[0052] The beginning segment 12 c of the extension 12 has acircumferential latch 14, which is formed in the manner of an annularshoulder and is likewise spaced from the support surface 12 d of theextension 12 that cooperates with the front side 2 b.

[0053] The ability of the extension 12 to be elastically deformed allowsit to be displaced relative to the tool guide 2 such that its latch 14extends into the region of the annular-groove-like depression 13 andlatches in the depression 13, thereby forming the aforementioneddetachable connection.

[0054] The elastic deformability of the extension 12 maintains theconnection formed in this manner between the receiving segment 2 a andthe beginning segment 12 c as long as no external forces larger than theholding force that originates from the extension act upon the extension12.

[0055] If tool breakage occurs in the region of the extension 12, theextension can first be deformed due to the effect of the transverseforces, or if the stress is excessive, it can detach from the receivingsegment 2 a of the tool guide 2, which may prevent damage at least tothe tool guide 2. Depending on the effects of the relevant malfunction,the detached extension 12 may be reused, that is, latched again with thereceiving segment 2 a.

[0056] If necessary, within the scope of the invention, the connectionbetween the receiving segment 2 a and the beginning segment 12 c may befurther reinforced through the selection of the height of thecircumferential (seen parallel to the longitudinal axis 3 a) latch 14 inthe disassembled state to be larger than the height of theannular-groove-like recess 13 in the described direction (see FIG. 2 inparticular). Accordingly, the latch 14 is compressed when brought intothe depression 13, so the latch is also held with a non-positive lockupin the receiving segment 2 a.

[0057] In addition to or instead of this measure, the subject of theinvention can also be embodied such that the annular groove formedbetween the latch 14 and the front side 12 d forms a non-positive lockupwith the receiving segment 2 a.

[0058] As can be seen from FIGS. 1 and 2, the annular-groove-likedepression 13 is disposed on the inside of the tool guide 2 facing thechisel 3. Furthermore, the effective inner diameter of the tool guide 2and the inner diameter of the extension 12 in the region of itsbeginning segment 12 c are adapted to one another such that the toolguide 2 changes over into the extension 12, thereby forming a shoulderA. With the exception of the beginning segment 12 c in the region of thereceiving segment 2 a, the wall thickness of the extension decreasescontinuously in the direction of the end segment 12 a, with a constantouter diameter.

[0059] This ensures that the extension 12 is located outside of theworking region of the percussive tool 3 in the normal state (FIG. 1),and may be able to detach from the receiving segment 2 a of the toolguide 2.

[0060]FIG. 3 illustrates an embodiment of the invention in which thereceiving segment 2 a of the tool guide 2 is provided with anannular-groove-like depression 15 that is undercut in the direction ofthe guide (toward the top in the drawing). As already explained inconjunction with FIGS. 1 and 2, the depression is disposed on the insideof the tool guide 2 facing the percussive tool 3, and thus thelongitudinal axis 3 a.

[0061] Because of the aforementioned undercut, the depression 15 has anannular, circumferential shoulder 2 c in the direction of thelongitudinal axis 3 a. Accordingly, the opening of the depression 15(seen parallel to the longitudinal axis 3 a) is smaller than the totalheight in the described direction.

[0062] The beginning segment 12 c of the extension 12 is provided with acircumferential latch 16 that is spaced from the front side 12 d, and,seen in cross-section, is oriented essentially parallel to thelongitudinal axis 3 a.

[0063] The dimensions of the latch 16 parallel to the longitudinal axis3 a are shown in exaggerated form merely for illustration purposes. Ofcourse, the depression 15 and the latch 16 must be adapted to each otherin terms of size such that the latch 16 can be guided into thedepression 15 and retain the assumed latched position, thereby producingthe desired detachable connection, provided that no excessively highforces are exerted on the extension 12 and break the connection betweenthe receiving segment 2 a and the beginning segment 12 c.

[0064] If necessary, the receiving segment 2 a and the beginning segment12 c of the extension can be adapted to one another, especially in termsof the embodiment and dimensions of the depression 15 and the latch 16,such that the latch 16 is held in a non-positive lockup in the recess15.

[0065] Unlike in the embodiment shown in FIGS. 1 and 2, the extension 12forming an independent, elastic support element is formed such that itsinner diameter, with the exception of the beginning segment 12 c,increases continuously in the direction of the end segment 12 a, with aconstant wall thickness in the assembled state.

[0066] In the embodiment according to FIG. 4, the receiving segment 2 afor securing the elastic extension 12 has an annular-groove-likedepression 17, which is formed on the outside of the tool guide 2 facingaway from the percussive tool (FIG. 1), and is oriented transversely tothe longitudinal axis 3 a. The extension 12 is thus adapted to thereceiving segment 2 a such that its beginning segment 12 c has anannular latch 18 that projects in the direction of the longitudinal axis3 a and has an inclined edge 18 a for facilitating the process ofinserting the extension into the recess 17.

[0067] Because of the elastic deformability of the elastomer extension12, the latch 18 can be displaced so far past the front side 2 b in thedirection of the receiving segment 2 a that it eventually latches intothe annular-groove-like depression 17 and detachably connects theextension to the tool guide 2 via the beginning segment 12 c.

[0068] This connection may be broken if desired, or in the event of amalfunction, by exerting sufficient transverse forces onto the extension12.

[0069] If necessary, the connection produced between the segments 2 aand 12 c can be additionally supported by producing the latch 18 withexcess material, and fitting it into the depression 17 with anon-positive lockup.

[0070] Furthermore, the discussed connection can be additionallyreinforced by pushing a lock washer 19 onto the extension 12 from theoutside at the height of the depression 17. This lock washer 19additionally generates a force component that serves in keeping thelatch 18 inside the recess 17.

[0071] To prevent an undesired displacement of the lock washer 19, theextension 12 should have a corresponding element for securing itsposition, such as the annular groove 20 indicated in FIG. 4, whichreceives the lock washer 19.

[0072] The extension 12 is otherwise formed such that its cross-sectiondecreases continuously in the direction of the inner seal 11, with aconstant inner diameter.

[0073] The inner diameter of the tool guide 2 changes over in conicalfashion into the inner diameter of the extension 12 in the region of thereceiving segment 2 a.

[0074] The embodiment according to FIG. 5 differs from theabove-described embodiment in that the receiving segment 2 a of the toolguide 2 has annular-groove-like depressions 17 and 21, which are spacedfrom one another, and in which the elastically deformable extension 12is detachably supported by annular latches 18 and 22, respectively.

[0075] As already explained in conjunction with FIG. 4, the connectionbetween the segments 2 a and 12 c may additionally be secured by pushinga securing element, preferably one that can be elastically deformed,onto the extension 12 at the height of the receiving segment 2 a andfixing it appropriately to avoid undesired movements parallel to thelongitudinal axis 3 a.

[0076] The holding device illustrated in FIG. 6 corresponds to the onein FIG. 3 insofar that the receiving segment 2 a likewise has anannular-groove-like depression 23, which is undercut in the direction ofthe tool guide 2 (toward the top in the drawing), and in which anannular latch 24 is supported in the assembled state. The latter can bepressed into the recess 23 with a corresponding prestress.

[0077] Unlike in the embodiment according to FIG. 3, theannular-groove-like depression 23 is formed on the outside of the toolguide 2 facing away from the percussive tool 3 (FIG. 1). Accordingly,the latch 24 also projects in the direction of the percussive tool 3, orthe longitudinal axis 3 a, inside the depression 23.

[0078] With the exception of the embodiment and arrangement of the latch24 in the region of the receiving segment 2 a, the elastic extension 12with the inner seal 11 secured thereto is formed identically to theembodiment shown in FIG. 4.

[0079] In the embodiment of the invention shown in FIG. 7, the receivingsegment 2 a of the tool guide 2 is provided with an annular-groove-likedepression 25, which is oriented transversely to the longitudinal axis 3a and is disposed on the outside of the tool guide 2. In the assembledstate, an annular, circumferential latch 26 having an inclined edge 26 a(corresponding to the one in FIG. 4) projects into this depression 25.

[0080] The receiving segment 2 a further has an annular-groove-likefront-side depression 27 that originates from the front side 2 b andbecomes wider, that is, it is undercut, in the direction of the toolguide 2 (toward the top in the drawing).

[0081] Corresponding to the embodiment of the receiving segment 2 a, thebeginning segment 12 c of the extension 12 is provided with a furtherannular latch 28, which has a head part 28 a with two holding surfaces28 b.

[0082] In the illustrated assembled state, the head part is fixed insidethe widened part of the front-side depression 27 by the holding surfaces28 b.

[0083] The above-described holding device thus results from acombination of a latch 26 and a latch 28 that latch laterally and at thefront side, respectively, in adapted, annular-groove-like depressions.

[0084] The particular advantage attained with the invention is that thetool guide provides more extensive protection against damage than beforethrough the embodiment of the extension that supports the inner seal asan independent support element. The extension represents a relativelylow-cost exchangeable part whose elastic deformability allows it toproduce and maintain a detachable connection with the tool guide,provided that the extension is not acted upon by unacceptably highexternal forces.

[0085] In the event of a malfunction, the extension can detach from thetool guide, which may avoid further damage to the tool guide and,possibly, to the extension itself.

[0086] The invention now being fully described, it will be apparent toone of ordinary skill in the art that many changes and modifications canbe made thereto without departing from the spirit or scope of theinvention as set forth herein.

What is claimed is:
 1. An apparatus comprising: a fluid-operatedpercussion drive; a housing part that shields the percussion drive, atleast at the front, against the environment, and into which a percussivetool driven by the drive projects axially into a tool guide of thedrive; an exchangeable outer seal disposed at an opening provided in thehousing part for the tool, with the seal surrounding the tool,transversely to its longitudinal axis, with at least some spacing, andbeing seated for movement in the transverse direction; an inner sealdisposed behind the outer seal, when seen counter to the direction ofaction of the tool, and resting in an elastic manner against the tool,outside of said guide, with the inner seal being secured, so as to beexchangeable, to an axial extension of the tool guide in the directionof the action of the tool, said extension surrounding the percussivetool in the region of the inner seal, with a spacing that is larger thanthe largest possible transverse displacement of the percussive tool inthe housing; and wherein: said extension is an independent, elasticsupport element that, on its rear side facing away from the inner seal,has a beginning segment that forms a detachable connection with areceiving segment of the tool guide in the longitudinal and transversedirections; and the extension latches in the receiving segment of thetool guide that is designed to secure the extension in a snapconnection.
 2. The apparatus according to claim 1, wherein the extensionis formed of a thermoplastic elastomer.
 3. The apparatus according toclaim 2, wherein the thermoplastic elastomer is polyurethane.
 4. Theapparatus according to claim 1, wherein the connection is produced atleast partially inside the tool guide.
 5. The apparatus according toclaim 1, wherein the extension is supported on the outside of the toolguide facing away from the percussive tool.
 6. The apparatus accordingto claim 1, wherein the tool guide has at least one annular-groove-typedepression as a component of the connection.
 7. The apparatus accordingto claim 6, wherein the at least one annular-groove-type depression isformed on the outside of the tool guide facing away from the percussivetool.
 8. The apparatus according to claim 6, wherein theannular-groove-type depression is additionally undercut, at least on oneof the side facing the inner seal and the side facing away from theinner seal.
 9. The apparatus according to claim 7, wherein theannular-groove-type depression is additionally undercut, at least on oneof the side facing the inner seal and the side facing away from theinner seal.
 10. The apparatus according to claims 6, wherein theannular-groove-type depression is formed as a front-side depression thatoriginates on the front side of the tool guide that faces the innerseal.
 11. The apparatus according to claim 10, wherein the front-sidedepression is undercut in the direction of the tool guide.
 12. Theapparatus according to claim 1, wherein the extension is additionallyheld in position in the direction of the receiving segment of the toolguide by at least one annular securing element.
 13. The apparatusaccording to claim 1, wherein the extension has at least one annularlatch that extends into the receiving segment of the tool guide.
 14. Theapparatus according to claim 13, wherein at least one latch of theextension is supported in a non-positive lockup on the receivingsegment.
 15. The apparatus according to claim 1, wherein the wallthickness of the extension, with the exception of the beginning segmentthat produces the connection, and its end segment, that supports theinner seal, decreases in the direction of the end segment.
 16. Theapparatus according to claim 1, wherein an inner diameter of the endsegment of the extension that supports the inner seal is larger than aninner diameter of its beginning segment that produces the connection.